The FBI has determined that there was no foul play involved in the Connecticut commuter train crash in which at least 70 people were injured, officials said today.

Instead, National Transportation Safety Board investigators are looking into a fractured rail as a possible cause of the derailment that led to two commuter trains to crashing head-on during the Friday rush hour.

"[The FBI] decided that they were was no foul play and they have since removed themselves from the investigation," NTSB member Earl Weener said.

He said they've begun inspecting the rail near the Metro-North train accident that occurred just outside Bridgeport, Conn., and found a fracture of interest to investigators.

"There was a section of rail in the eastbound track that part of the rail going toward New Haven that was fractured at a rail joint," Weener said. "It could have been caused by the accident itself or it could have been broken at the time of the accident. It could have been broken prior to the accident."

Investigators from the NTSB arrived at the scene this morning to begin surveying the twisted rail cars that remained on the tracks.

Weener said that in addition to the physical evidence, they were "looking at how the crew behaved and how the crew operated the train."

During the investigation, which is expected to last seven to 10 days, officials will also examine the braking performance of the trains and the conditions of the wheels, cars and track to see if they played a role in the crash, Weener said.

Gov. Dannel Malloy said three people remained in critical condition today, while five others also remained hospitalized for their injuries. Many of the injured suffered bruises, cuts and minor fractures and were able to be treated and released, according to officials at two area hospitals.

A Metro-North train was traveling east from New York City's Grand Central Station to New Haven, Conn., when it derailed at 6:10 p.m., Weener said.

The jolt of the impact was so strong, passengers said it caused bodies to be flung around the cars.

"All I know was I was in the air, hitting seats, bouncing around, flying down the aisle and finally I came to a stop on one seat," Lola Oliver, 49, of Bridgeport, told The Associated Press. "It happened so fast I had no idea what was going on. All I know is we crashed."

Sen. Richard Blumenthal, D-Conn., was among the elected officials who surveyed the damage and called the scene "absolutely staggering."

He said the injuries could have been much worse and lauded the investment in infrastructure for saving lives.

"Investment in quality of transportation is probably one of the lessons we will learn from this accident," he said.

While the wreckage remains on the tracks, transportation in the Northeast Corridor is expected to be crippled.

Two of the tracks on the line were already out of service for a project, and the remaining two open tracks the trains were damaged in the collision, according to the Metropolitan Transportation Authority, which operates the Metro-North Railroad.

Amtrak's service between New York City and Boston, which operates on the tracks where the accident occurred, was also suspended indefinitely.

Commuting could be a challenge on Monday for those around Bridgeport who rely on Metro-North to get to and from work in New York City.

Malloy said a system was being set up to move people from Bridgeport to nearby train stations.